The present invention relates to a valve arrangement comprising a pressure control valve which is placed in a pressure duct between a source of fluid under pressure and a pressure system and is adapted to be used with a constant pressure range that is to be maintained, said pressure control valve being adapted to be controlled in response to a pressure sensor.
Such valve arrangements are utilized to maintain a constant pressure range in a pressure system, the pressure control valve opening when the pressure in the system has sunk below a preset pressure and closing when the desired pressure has been reached again. On opening the pressure control valve it is possible for fluid under pressure to continue flowing from the pressure fluid source into the pressure system so that an increase in pressure is brought about.
A disadvantage in connection with this type of prior art valve arrangement is that the response sensitivity is insufficient and that hunting of the pressure control valve around the pressure response value is excessive so that an excessive amount of fluid under pressure escapes owing to venting of the valve or valves from the system, this being more particularly objectionable if the fluid to be controlled is used for operation of the valves and if such fluid is corrosive, evil-smelling or even toxic. Another shortcoming is often to be seen in the fact that the individual components are arranged so that it is difficult to see how they are functionally connected, long leads being needed which make assembly complex and render the system liable to failure.